Solid-state imaging device and imaging system

ABSTRACT

A solid-state imaging device includes: a first semiconductor substrate including a photoelectric conversion element; and a second semiconductor substrate including at least a part of a peripheral circuit arranged in a main face of the second semiconductor substrate, the peripheral circuit generating a signal based on the charge of the photoelectric conversion element, a main face of the first semiconductor substrate and the main face of the second semiconductor substrate being opposed to each other with sandwiching a wiring structure therebetween; a pad to be connected to an external terminal; and a protection circuit electrically connected to the pad and to the peripheral circuit, wherein the protection circuit is arranged in the main face of the second semiconductor substrate.

TECHNICAL FIELD

The present invention relates to a solid-state imaging device and, inparticular, to a pad part thereof.

BACKGROUND ART

In a charge-coupled device (CCD) type or an amplification typesolid-state imaging device used in a digital still camera, a cam coderor the like, there is a demand for finer pixels to obtain a highdefinition image. However, the finer the pixels, the smaller the lightreceiving area of a photoelectric conversion element for detecting lightincluded in the pixels, resulting in a reduction in sensitivity.

Japanese Patent Application Laid-Open No. 2006-191081 discussescomplementary metal-oxide-semiconductor (CMOS) type, which is also anamplification type, solid-state imaging device of a construction inwhich a first substrate with a photoelectric conversion element and atransfer transistor arranged thereon and a second substrate with anothercircuit arranged thereon are bonded to each other to form a solid-stateimaging device to secure the requisite light receiving area of thephotoelectric conversion element.

Further, Japanese Patent Application Laid-Open No. 2006-191081 discussesa solid-state imaging device in which a connection portion extendingthrough a second substrate is connected to an input/output pad to effectconnection of the input/output pad from the back-side of the secondsubstrate. This input/output pad is formed after the connection portionis exposed by polishing of the second substrate.

However, Japanese Patent Application Laid-Open No. 2006-191081 discussesa construction in which the input/output pad is directly connected tothe circuit of the first substrate. In such a construction, externalnoise from an external terminal is imparted to the circuit of the firstsubstrate, so that a malfunction of the circuit can be generated.Further, a photoelectric conversion element is arranged on the firstsubstrate, and incorporation of external noise may affect the imagesignal.

CITATION LIST Patent Literature

-   PTL 1: Japanese Patent Application Laid-Open No. 2006-191081

SUMMARY OF INVENTION

The present invention is directed to reduce a incorporation of anexternal noise from a pad into a photoelectric conversion element.

According to an aspect of the present invention, a solid-state imagingdevice includes: a first semiconductor substrate including aphotoelectric conversion element; and a second semiconductor substrateincluding at least a part of a peripheral circuit arranged in a mainface of the second semiconductor substrate, the peripheral circuitgenerating a signal based on the charge of the photoelectric conversionelement, a main face of the first semiconductor substrate and the mainface of the second semiconductor substrate being opposed to each otherwith sandwiching a wiring structure therebetween; a pad to be connectedto an external terminal and a protection circuit electrically connectedto the pad and to the peripheral circuit, wherein the protection circuitis arranged in the main face of the second semiconductor substrate.

According to the present invention, it is possible to mitigateincorporation of external noise from the pad into the photoelectricconversion element.

Further features and aspects of the present invention will becomeapparent from the following detailed description of exemplaryembodiments with reference to the attached drawings.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate exemplary embodiments, features,and aspects of the invention and, together with the description, serveto explain the principles of the invention.

FIG. 1 is a schematic sectional view of a solid-state imaging deviceaccording to a first exemplary embodiment.

FIG. 2A is a schematic plan view of the solid-state imaging device ofthe first exemplary embodiment.

FIG. 2B is a schematic plan view of the solid-state imaging device ofthe first exemplary embodiment.

FIG. 3 is a circuit diagram of the solid-state imaging device of thefirst exemplary embodiment.

FIG. 4A is a schematic sectional view illustrating a method ofmanufacturing the solid-state imaging device of the first exemplaryembodiment.

FIG. 4B is a schematic sectional view illustrating a method ofmanufacturing the solid-state imaging device of the first exemplaryembodiment.

FIG. 5A is a schematic sectional view illustrating a method ofmanufacturing the solid-state imaging device of the first exemplaryembodiment.

FIG. 5B is a schematic sectional view illustrating a method ofmanufacturing the solid-state imaging device of the first exemplaryembodiment.

FIG. 6A is a schematic sectional view illustrating a method ofmanufacturing the solid-state imaging device of the first exemplaryembodiment.

FIG. 6B is a schematic sectional view illustrating a method ofmanufacturing the solid-state imaging device of the first exemplaryembodiment.

FIG. 7A is a schematic sectional view of a solid-state imaging deviceaccording to a second exemplary embodiment.

FIG. 7B is a schematic sectional view of a solid-state imaging deviceaccording to a second exemplary embodiment.

FIG. 8A is a schematic sectional view illustrating a solid-state imagingdevice according to a third exemplary embodiment and a method ofmanufacturing the same.

FIG. 8B is a schematic sectional view illustrating a solid-state imagingdevice according to a third exemplary embodiment and a method ofmanufacturing the same.

FIG. 8C is a schematic sectional view illustrating a solid-state imagingdevice according to a third exemplary embodiment and a method ofmanufacturing the same.

FIG. 9 is a schematic sectional view of a solid-state imaging deviceaccording to a fourth exemplary embodiment.

FIG. 10A is a circuit diagram of a protection diode.

FIG. 10B is a schematic plan view of a protection diode.

FIG. 11A is a circuit diagram of a protection diode.

FIG. 11B is a circuit diagram of a protection diode.

DESCRIPTION OF EMBODIMENTS

Various exemplary embodiments, features, and aspects of the inventionwill be described in detail below with reference to the drawings.

A solid-state imaging device according to the present inventioncomprises a first semiconductor substrate including a photoelectricconversion element, and a second semiconductor substrate including atleast a part of a peripheral circuit. The peripheral circuit is forgenerating a signal based on the charge of the photoelectric conversionelement and is arranged in a main face thereof. A main face of the firstsemiconductor substrate and the main face of the second semiconductorsubstrate are opposed to each other with sandwiching a wiring structuretherebetween. The solid-state imaging device comprises a pad to beconnected to an external terminal, and a protection circuit electricallyconnected to the pad and to the peripheral circuit. The protectioncircuit is arranged in the main face of the second semiconductorsubstrate. By thus arranging the protection circuit on the secondsubstrate, it is possible to mitigate incorporation of external noisefrom the external terminal and to protect a circuit on a succeedingstage. Further, it is possible to suppress the incorporation of theexternal noise from the external terminal into the photoelectricconversion element.

In the following, the present invention will be described in detail withreference to the drawings. In the description of the exemplaryembodiments, the main face of the first substrate and the main face ofthe second substrate are the front-side faces of the substrates on whichtransistors are formed. The faces on the opposite side of the main faces(front-side faces) are the back-side face of the first substrate and theback-side face of the second substrate. The upward direction is from theback-side face toward the main face (front-side face), and the downwarddirection and the depth direction are direction from the main face(front-side face) toward the back-side face of the substrate.

The first exemplary embodiment of the present invention will bedescribed with reference FIGS. 1 through 6B. In the present exemplaryembodiment, a protection diode circuit is used as the protectioncircuit.

First, the circuit of the solid-state imaging device of the firstexemplary embodiment will be described with reference to FIG. 3. In thepresent exemplary embodiment described below, the signal chargeconsists, for example, of electrons. The solid-state imaging device ofFIG. 3 includes a pixel part 301 in which a plurality of photoelectricconversion elements are arranged. Further, the solid-state imagingdevice includes a peripheral circuit part 302 where there is arranged aperipheral circuit that may include a reading circuit configured to reada signal from the pixel part 301, a control circuit for driving thereading, and a signal processing circuit configured to process the readsignal.

In the pixel part 301, there are arranged a plurality of photoelectricconversion elements 303, transfer transistors 304, amplificationtransistors 306, and reset transistors 307. A pixel is configured with aconstitution including at least one photoelectric conversion element.One pixel of the present exemplary embodiment includes a photoelectricconversion element 303, a transfer transistor 304, an amplificationtransistor 306, and a reset transistor 307. The anode of thephotoelectric conversion element 303 is grounded. The source of thetransfer transistor 304 is connected to the cathode of the photoelectricconversion element 303, and the drain region of the transfer transistor304 is connected to the gate electrode of the amplification transistor306. A node that is identical with the gate electrode of theamplification transistor 306 will be referred to as a node 305. Thereset transistor is connected to the node 305, and sets the potential ofthe node 305 to an arbitrary potential (e.g., reset potential). Theamplification transistor 306 is a part of a source follower circuit, andoutputs a signal according to the potential of the node 305 to a signalline RL. In some cases, the node 305 is also referred to as a floatingdiffusion. A circuit including the transfer transistor 304, theamplification transistor 306, and the reset transistor 307 is a pixelcircuit.

The peripheral circuit part 302 represents the region other than thepixel part 301. In the peripheral circuit part 302, there is arranged aperipheral circuit including a readout circuit and a control circuit.The peripheral circuit has a vertical scanning circuit VSR, which is acontrol circuit for supplying a control signal to the gate electrode ofeach transistor of the pixel part 301. Further, the peripheral circuithas a readout circuit RC configured to retain a signal output from thepixel part 301 and to perform signal processing such as amplification,addition, and analog-digital (AD) conversion. Further, the peripheralcircuit has a horizontal scanning circuit HSR, which is a controlcircuit configured to control the timing with which signals aresuccessively output from the readout circuit RC. By operating theperipheral circuit, there is generated a signal according to a signaloutput from the signal line RL of the pixel circuits. Naturally, thissignal is a signal based on the charge of each photoelectric conversionelement 303.

The solid-state imaging device of the first exemplary embodiment isformed by bonding two members to each other. The two members consist ofa first member 308 including a first substrate 101 and a second member309 including a second substrate 121. The first substrate 101 includesthe photoelectric conversion elements 303 and the transfer transistors304 of the pixel part 301, and, the second substrate 121 includes theamplification transistors 306 and the reset transistors 307 of the pixelpart 301 and the peripheral circuit part 302. A control signal issupplied from the peripheral circuit part 302 of the second member 309to the gate electrode of each transfer transistor 304 of the firstmember 308 via a connection portion 310. The construction of theconnection portion 310 will be described below. A signal generated byeach photoelectric conversion element 303 of the first member 308 isread out at the drain region of each transfer transistor 304, that is,at each node 305. Each node 305 includes a structure arranged on thefirst member 308 and a structure arranged on the second member 309.

Owing to this construction, as compared with the conventional case wherethe entire pixel part is arranged on one member (that is, on onesubstrate), it is possible to increase the area of the photoelectricconversion elements 303, enabling to achieve an improvement in terms ofsensitivity. Further, as compared with the conventional case where theentire pixel part is arranged on one member (that is, on one substrate),it is possible to provide more photoelectric conversion elements of thesame area, enabling to increase the number of pixels. At least thephotoelectric conversion elements are necessary to be arranged on thefirst substrate, and the amplification transistors 306 may be arrangedon the first substrate. Further, the photoelectric conversion elementsand the gate electrodes of the amplification transistors can beconnected to each other without providing the transfer transistors. Inthe present invention, the elements arranged on the first substrate canbe arbitrarily selected, and the construction of the pixel circuit alsocan be arbitrarily selected.

A specific plan layout of such a solid-state imaging device will bedescribed with reference to FIGS. 2A and 2B, which are schematic planviews of a solid-state imaging device. FIG. 2A illustrates the planlayout on the first member 308, that is, the first substrate (101), andFIG. 2B illustrates the plan layout of the second member 309, that is,the second substrate (121).

In FIG. 2A, on the first member 308, there are arranged a pixel part301A in which a plurality of photoelectric conversion elements arearranged, and a pad part 312A where pads 313 are arranged. In the pixelpart 301A, there are arranged a plurality of photoelectric conversionelements 303, transfer transistors 304, and connection portions 310 and311 as illustrated in FIG. 3. In the pad part 312A, there is arranged aconnection portion 314A for connection with the second member 309 at thesame position in a planar direction as the pads 313. An externalterminal is to be connected to the pads 313. An example of the externalterminal is a bonding wire connected to the pads 313 by the wire bondingmethod. In the solid-state imaging device, there are arranged aplurality of pads 313, which include a pad (output pad) for outputting asignal (image signal) based on the charge generated by the photoelectricconversion elements, and a pad (input pad) to which a voltage suppliedfrom the outside to drive the peripheral circuit, for example, is input.

Next, in FIG. 2B, there are arranged on the second member 309 a pixelpart 301B, the peripheral circuit part 302B, and a pad part 312B. A partof the pixel circuits is arranged in the pixel part 301B; a plurality ofamplification transistors 306, reset transistors 307, connectionportions 310, and connection portions 311 as illustrated in FIG. 3 arearranged. In the peripheral circuit part 302B, there are arranged thehorizontal scanning circuit HSR, the vertical scanning circuit VSR, andthe readout circuit RC. In the pad part 312B, there are arranged aconnection portion 314B for connection with the first member, and aprotection diode circuit 315. As will be illustrated in detail withreference to FIG. 1, the connection portion 314 B is arranged at thesame position in a planar direction as the protection diode circuit 315.Owing to the arrangement of the protection diode circuit 315, it ispossible to mitigate incorporation of external noise from the externalterminal. Further, it is possible to protect the circuit on thesucceeding stage against erroneous input and surge voltage. Theprotection diode circuit 315 is electrically connected to the peripheralcircuit. More specifically, as illustrated in FIG. 2B, there areprovided a plurality of protection diode circuits 315, and theprotection diode circuit 315 connected to each pad 313 is connected to avertical scanning circuit VSR, a horizontal scanning circuit HSR, or areadout circuit RC. And, by arranging the protection diode circuits 315on the second member 309, it is possible to reduce transmission ofexternal noise to the photoelectric conversion element. Further, when anabnormal signal is generated within the solid-state imaging device, theprotection diode circuit 315 connected to the output pad will be able tosuppress the output of this abnormal signal to the exterior of thedevice.

And, the solid-state imaging device of the present exemplary embodimentis formed by bonding together the first member 308 and the second member309 of the plan layout as illustrated in FIGS. 2A and 2B. Morespecifically, the arrangement is made such that the pixel part 301A andthe pixel part 301B overlap each other. And, the connection portion 314Aand the connection portion 314B are connected to each other, and theconnection portion 310 and the connection portion 311 of the firstmember and the connection portion 310 and the connection portion 311 ofthe second member are connected to each other. In FIGS. 2A and 2B, theregion of the first member 308 corresponding to the peripheral circuitpart 302B of the second member 309 is indicated as the peripheralcircuit part 302A. A part of the scanning circuit, that is, a part ofthe peripheral circuit, may be arranged in the peripheral circuit part302A.

The construction of the protection diode circuit 315 will be describedwith reference to FIGS. 10A and 10B and FIGS. 11A and 11B. FIG. 10A is acircuit diagram illustrating a certain protection diode circuit, andFIG. 10B is a diagram illustrating a plan layout corresponding thereto.FIGS. 11A and 11B are circuit diagrams illustrating a protection diodecircuit of a different construction from that of FIGS. 10A and 10B.Regarding the plan layout of the protection diode circuit of FIGS. 11Aand 11B, a description thereof will be omitted. In the present exemplaryembodiment, protection diode circuits as illustrated in FIGS. 10A and10B and FIGS. 11A and 11B are appropriately selected and provided as theplurality of protection diode circuits 315 illustrated in FIGS. 2A and2B.

The protection diode circuit illustrated in FIG. 10A has an inputterminal IN and an output terminal OUT, two resistors (hereinafterreferred to as a first resistor 147 and a second resistor 148), and twodiodes (hereinafter referred to as a first diode 145 and a second diode146). In the protection diode circuit, the input terminal and a terminalof the resistor 147 are connected to each other, and the other terminalof the first resistor 147 is connected to the anode of the first diode145, the cathode of the second diode 146, and a terminal of the secondresistor 148. And, the other terminal of the second resistor 148 isconnected to the output terminal. In other words, at a node 149, theother terminal of the first resistor 147, the anode of the first diode145, the cathode of the second diode 146, and a terminal of the secondresistor 148 are connected to each other. The cathode of the first diode145 is connected to a predetermined voltage (VDD), and the anode of thesecond diode 146 is connected to another voltage (VSS) different fromthe predetermined voltage. Here, the voltages are in the followingrelationship: VDD>the voltage at the input terminal IN>VSS. It is onlynecessary for the voltage VSS to be a voltage lower than the voltageVDD; as indicated by a circuit symbol in FIG. 10A, it may be a groundingvoltage (GND).

Owing to this circuit form, when, for example, there is input to theinput terminal IN a voltage larger than the sum total of the voltage VDDand the forward voltage drop at the first diode 145, a forward bias isapplied to the first diode 145, and an electric current flows from thenode 149 to VDD. Thus, it is possible to prevent application to thecircuit on the succeeding stage of a voltage larger than the sum totalof VDD and the forward voltage drop at the first diode 145. When thereis input to the input terminal IN a voltage smaller than the differencebetween VSS and the forward voltage at the second diode 146, a forwardbias is applied to the second diode 146, and electric current flows fromVSS to the node 149. Thus, it is possible to prevent application to thecircuit on the succeeding stage of a voltage smaller than the differencebetween VSS and the forward voltage at the second diode 146. Further theresistors 147 and 148 serve to lower the input voltage and to reduce theabsolute value of the voltage applied to the output side.

Next, FIG. 10B is a corresponding plan view. A contact is indicated by asquare. The contact is included in a contact layer. First, elementseparation structures 136 are arranged in the protection diode circuit.The input terminal IN consisting of wiring included in a wiring layer130 is connected to the first resistor 147 consisting of wiring includedin a gate electrode layer 128. The other terminal of the first resistor147 is connected to wiring 150 of the wiring layer 130 via the contact.The wiring 150 is connected to a p-type semiconductor region 902 formingthe anode of the first diode 145 via the contact, and is connected to ann-type semiconductor region 903 forming the cathode of the second diode146 via the contact. And, the wiring layer 150 is connected to thesecond resistor 148 consisting of wiring included in the gate electrodelayer 128 via the contact. In other words, the node 149 of FIG. 10A isformed by the wiring 150, the first resistor 147, the second resistor148, the p-type semiconductor region 902, and the n-type semiconductorregion 903 of FIG. 10A and the contact connecting them together. And,the n-type semiconductor region 901 constituting the cathode of thefirst diode 145 is included in the wiring layer 130, and is connected towiring VDD supplying the predetermined voltage (VDD) via a plurality ofcontacts. The p-type semiconductor region 904 constituting the anode ofthe second diode 146 is included in the wiring layer 130, and isconnected to the wiring VSS supplying the predetermined voltage (VSS)via a plurality of contacts. Here, each diode is surrounded by theelement separation structure 136, and, even if there is generated afluctuation due to a signal input, it is possible to mitigate theinfluence thereof on the other circuits. Further, to achieve animprovement in terms of withstand voltage between the semiconductorregions, the element separation structure 136 is also provided betweenthe semiconductor regions constituting the anode and the cathode and thecontact for supplying voltage thereto.

The protection diode circuit of FIG. 11A is composed of an inputterminal IN, an output terminal OUT, and one diode 1101; the anode ofthe diode 1101 is connected to the input terminal IN and the outputterminal OUT, with the cathode being connected to a predeterminedvoltage (VDD). The protection diode circuit of FIG. 11B is composed ofan input terminal IN, an output terminal OUT, and one diode 1102; thecathode of the diode 1102 is connected to the input terminal IN and theoutput terminal OUT, and the anode thereof is connected to apredetermined voltage (voltage VSS lower than the voltage VDD).

In the present exemplary embodiment, the protection diode circuit ofFIG. 11A is arranged in correspondence with a pad to which apredetermined voltage (the voltage VSS that is lower than the voltageVDD) is input. The protection diode circuit of FIG. 11B is arranged incorrespondence with a pad to which a predetermined voltage (the voltageVDD that is higher than the voltage VSS) is input. The protection diodecircuit of FIGS. 10A and 10B is arranged in correspondence with a pad toor from which another signal is input or output. As needed, theprotection diode circuit of FIGS. 10A and 10B may be arranged incorrespondence with the input pad, and the protection diode circuit ofFIG. 11A or 11B may be arranged in correspondence with the output pad.As described above, external noise is caused, for example, by erroneousinput, voltage surge, etc. In particular, from the viewpoint ofprotecting the peripheral circuit from voltage surge generated byelectro-static discharge (ESD), it is very meaningful to arrange theprotection diode circuit 315 on the second substrate 121. Thepossibility of incorporation of voltage surge due to electro-staticdischarge is high regardless of whether it is an input pad or an outputpad, so that it is desirable for the protection diode circuit to bearranged in correspondence with both the input pad and the output pad.Of course, it is also possible to apply a structure different from thoseof the above three kinds of protection diode circuit to the protectiondiode circuit 315 of the present exemplary embodiment. For example, theresistors 147 and 148 may be formed solely by resistance of metalwiring; the resistors 147 and 148 may not be provided; and VSS may beconnected to other than GND.

Next, the solid-state imaging device illustrated in the schematicsectional views of FIGS. 2A, 2B, and 3 will be described with referenceto FIG. 1. In FIG. 1, the components that are the same as those of FIGS.2A, 2B, and 3 are denoted by the same reference numerals, and adescription thereof will be omitted.

The first member 308 includes the first wiring structure 149 and thefirst substrate 101. The first substrate 101 is configured with, forexample, of a silicon semiconductor substrate, and has a main face 102and a back-side face 103. A transistor is arranged in the main face 102of the first substrate. The first wiring structure 149 includesinter-layer insulating films 104 through 106, a gate electrode layer 107including a gate electrode and wiring, wiring layers 109 and 111including a plurality of wirings, and contact layers 108 and 110including a plurality of contacts or vias. Here, the number of layers ofthe inter-layer insulating films, of the wiring layers, and of thecontact layers included in the first wiring structure 149 may bearbitrarily set. The wiring layer 111 of the first wiring structure 149includes a connection portion.

In the pixel part 301 of the first member 308, there are arranged on thefirst substrate 101 an n-type semiconductor region 112 constituting aphotoelectric conversion element, an n-type semiconductor region 114constituting the drain of a transfer transistor, and an elementseparation structure 119. The transfer transistor is formed by then-type semiconductor region 112, the n-type semiconductor region 114,and a gate electrode 113 included in the gate electrode layer 107. Here,the charge accumulated in the n-type semiconductor region 112 istransferred to the n-type semiconductor region 114 by the gate electrode113. The potential based on the charge transferred to the n-typesemiconductor region 114 is transmitted to the second member 309 via acontact of the contact layer 108, wiring of the wiring layer 109, a viaof the contact layer 110, and wiring of the wiring layer 111. The wiringof the wiring layer 111 constitutes the connection portion 311. Thephotoelectric conversion element may be an embedded photo diode furtherincluding a p-type semiconductor region, or a photo gate, thus allowingmodification as appropriate.

On the back-side face 103 side of the first substrate 101 of the pixelpart 301, there arranged a planarization layer 115, a color filter layer116 including a plurality of color filters, a planarization layer 117,and a micro lens layer 118 including a plurality of micro lenses in thisorder. In FIG. 1, each of the plurality of color filters and of theplurality of micro lenses is arranged in correspondence with onephotoelectric conversion element, that is, for each pixel; however, itis also possible for one color filter and one micro lens to be providedfor a plurality of pixels. The solid-state imaging device of the presentexemplary embodiment is a back-side face irradiation type solid-stateimaging device in which light enters from the micro lens layer 118 sideand is received by the photoelectric conversion element.

In the pad part 312 of the first member 308, there are arranged a pad313 and an opening 100 through which the pad for connection to anexternal terminal is exposed. Further, there is arranged a connectionportion 314A configured to conduct a voltage input from the pad 313 tothe second member 309. The connection portion 314A is arranged at thesame position in a planar direction as the pad 313. In the first member308, in a region corresponding to the peripheral circuit part 302 of thesecond member 309, there is provided an arbitrary circuit element 120 asillustrated in FIG. 1.

The second member 309 has a second wiring structure 150 and a secondsubstrate 121. The second substrate 121 is configured with, for example,of a silicon semiconductor substrate, and has a main face 122 and aback-side face 123. A transistor is arranged on the main face 122 of thesecond substrate. The second wiring structure 150 has inter-layerinsulating films 124 through 127, a gate electrode layer 128 including agate electrode and wiring, wiring layers 130, 132, and 134 including aplurality of wirings, and contact layers 129, 131, and 133 including aplurality of contacts or vias. Here, the number of layers of theinter-layer insulating films, of the wiring layers, and of the contactlayers included in the second wiring structure 150 can be arbitrarilyset. The wiring layer 134 includes a connection portion.

In the pixel part 301 of the second member 309, there are arranged awell 135 constituting an amplification transistor of a pixel circuit, ann-type semiconductor region 138 constituting the source/drain region ofthe amplification transistor, and an element separation structure 136,in the second substrate 121. The amplification transistor is arranged inthe well 135, and is formed by a gate electrode 137 included in the gateelectrode layer 128, and an n-type semiconductor region 138 constitutinga source/drain region. Here, the connection portion 311 of the firstmember 308 and the gate electrode 137 of the amplification transistorare connected to each other via the wiring of the wiring layer 134, avia of the contact layer 133, the wiring of the wiring layer 132, a viaof the contact layer 131, the wiring of the wiring layer 130, and thecontact of the contact layer 129. The node 305 of FIG. 3 is composed ofthe n-type semiconductor region 114 of FIG. 1, the wirings of the wiringlayers 109, 111, 134, 132, and 130, the contacts or vias of the contactlayers 108, 110, 133, 131, and 129, and the gate electrode 137. Anothercircuits of the pixel part 301 (e.g., a reset transistor) are notillustrated.

Next, in the peripheral circuit part 302 of the second member 309, thereis arranged at least a part of a peripheral circuit including controlcircuits such as a horizontal scanning circuit and a vertical scanningcircuit and a readout circuit. FIG. 1 illustrates an n-type transistorand a p-type transistor of an arbitrary circuit included in theperipheral circuit. An n-type transistor consisting of a gate electrode140 included in the gate electrode layer 128 and an n-type source/drainregion 141 are arranged in a p-type well 139. And, a p-type transistorhaving a gate electrode 143 included in the gate electrode layer 128 anda p-type semiconductor region 144 constituting a p-type source/drainregion is arranged in an n-type well 142.

And, in the pad part 312 of the second member 309, there are arranged aprotection diode circuit 315 for inputting a signal from a pad 313 ofthe first member 308, and a connection portion 314B for connection withthe first member 308. The connection portion 314B is arranged at thesame position in a planar direction as the protection diode circuit 315.The protection diode circuit 315 has configuration of FIGS. 10A and 10B.Specifically, it includes two diodes 145 and 146 formed by semiconductorregions, and two resistors 147 and 148 formed by the gate electrodelayer 128. The input terminal IN, the output terminal OUT, and thewiring 150 are formed by the wiring constituting the wiring layer 130illustrated in FIG. 1. Further, the wirings of the first resistor 147and the second resistor 148 of FIG. 10B are configured with the wiringconstituting the electrode layer 128 illustrated in FIG. 1. Further, theprotection diode circuit 315 is arranged between the pad 313 connectedto the external terminal and the circuit of the peripheral circuit part302. Owing to this configuration, it is possible to suppress theexternal noise from the external terminal.

And, in the solid-state imaging device of the present exemplaryembodiment, the main face 102 of the first substrate 101 and the mainface 122 of the second substrate 121 are opposed to each other withsandwiching the first and second wiring structures therebetween(opposing arrangement). In other words, the first substrate, the firstwiring structure, the second wiring structure, and the second substrateare arranged in this order. Further, the upper face of the first wiringstructure 149 and the upper face of the second wiring structure 150 areto be regarded as bonded to each other at a bonding interface X. Thatis, the first member 308 and the second member 309 are bonded to eachother at the bonding interface X. The bonding interface X is formed bythe upper face of the first wiring structure 149 and the upper face ofthe second wiring structure 150. As a result, the first wiring structure149 and the second wiring structure 150 are integrated with each otherto form the wiring structure between the first substrate 101 and thesecond substrate 121. Here, in the bonding, it is possible to employ aconnection member such as a micro bonding in between, or to adopt metalbonding. Such bonding is achieved by the connection portion 311 and theconnection portion 314.

And, the pad 313 of the solid-state imaging device for signal exchangewith the exterior is arranged on top of the main face 122 of the secondmember 309, and an opening 100 is provided on the first member 308 side.And, the protection diode circuit 315 can be arranged inwardly withrespect to the pad 313 in planar direction which is parallel to the mainface 122. That is, from the end faces of the first substrate and thesecond substrate, the pad 311 and the protection diode circuit 315 arearranged in this order such that the protection diode circuit 315 ispositioned between the pad 311 and the peripheral circuit part. The pad313 and the protection diode circuit 315 can partially overlap eachother in planar direction. Owing to this construction, there is no needto provide an opening in the second member 309, so that it is possibleto suppress intrusion of water into the peripheral circuit part of thesecond member 309. Further, in the present exemplary embodiment, thenumber of elements arranged in proximity to the pad part of the firstmember 308 can be easily made smaller than the number of elementsarranged in proximity to the pad part of the second member 309. And, theelements arranged in proximity to the pad part of the first member 308can be more spaced apart from each other than the elements arranged inproximity to the pad part of the second member 309. Thus, it is possibleto further mitigate the influence of water from the opening 100 for thepads on the elements. Further, owing to the arrangement on the back-sideface side of the first member 308, the connection of the terminal to thepad 313 is facilitated, thereby reducing poor connection. Further, sincethe pad 313 and the protection diode circuit 315 overlap each other inplanar direction, it is possible to form the electrical connection fromthe pad 313 to the protection diode circuit 315 in a short distance.Further, the protection diode circuit 315 is formed on the second member309, that is, the second substrate 121. Suppose the protection diodecircuit 315 is arranged on the first substrate 101. Then, there is apossibility of external noise incorporating the photoelectric conversionelement, which is an analog circuit, if there occurs erroneous input orincorporation of external noise from the pad 313. Specifically, owing tothe configuration of the protection diode circuit of the presentinvention, it is possible to obtain a solid-state imaging device inwhich external nose is suppressed.

Next, a method of manufacturing the solid-state imaging device of thepresent exemplary embodiment will be described with reference to FIGS.4A, 4B, 5A, 5B, 6A, and 6B. FIGS. 4A and 4B are schematic sectionalviews illustrating the step of producing the first member 308, FIGS. 5Aand 5B are schematic sectional views illustrating the step of producingthe second member 309, and FIGS. 6A and 6B are schematic sectional viewsillustrating the manufacturing step after the bonding of the firstmember 308 and the second member 309.

The step of producing the first member 308 of FIG. 1 will be describedwith reference to FIGS. 4A and 4B. In FIGS. 4A and 4B, the structureconstituting the first member 308 of FIG. 1 layer is denoted by numeral308′, and the portions constituting the pixel part 301 of FIG. 1, theperipheral circuit part 302, the pad part 312, and the circuit element120, which is a part of the peripheral circuit, are respectively denotedby numerals 304′, 302′, 312′, and 120′.

First, a semiconductor substrate is prepared, and elements are formed onthe semiconductor substrate. A semiconductor substrate 401 of athickness D3 having a main face 402 and a back-side face 403 isprepared. The semiconductor substrate 401 is composed, for example, of asilicon semiconductor substrate. And element separation structure 119 isformed on the semiconductor substrate 401. The element separationstructure 119 includes an insulating member such as a silicon oxidefilm, and has, for example, a local-oxidation-of-silicon (LOCOS)structure or a shallow trench isolation (STI) structure. And, anarbitrary conductive type well (not illustrated) is formed in thesemiconductor substrate 401. After this, the n-type semiconductorregions 112 and 114 constituting the photoelectric conversion elementand the transistor and the p-type semiconductor region (not illustrated)are formed. Further, there is formed a gate electrode layer 107including the gate electrode 113 of the transfer transistor. The gateelectrode layer is formed by deposition and pattering of a poly siliconlayer, can include not only a gate electrode but also wiring. Regardingthe method of forming the gate electrode, the element separationstructure, and the semiconductor regions, it is possible to adopt ancommon semiconductor process, and a detailed description thereof will beomitted. By the above process, the configuration as illustrated in FIG.4A is obtained.

Next, a wiring structure is formed on the main face 402 of thesemiconductor substrate 401. The wiring structure has inter-layerinsulating films 104′, 105, and 106, contact layers 108 and 110, andwiring layers 109 and 111. The inter-layer insulating film 104′ layerconstitutes later the inter-layer insulating film 104 of FIG. 1. Theinter-layer insulating film 104′ covers the gate electrode layer 107,the contact layer 108 is arranged in the inter-layer insulating film104′, and the wiring layer 109 is arranged on the inter-layer insulatingfilm 104′. The inter-layer insulating film 105 covers the wiring layer109, the contact layer 110 is arranged in the inter-layer insulatingfilm 105, the wiring layer 111 is arranged on the inter-layer insulatingfilm 105, and the inter-layer insulating film 106 is arranged on theinter-layer insulating film 105 and has an opening through which thewiring of the wiring layer 111 is exposed. The upper face of the wiringstructure is formed by the upper face of the inter-layer insulating film106 and the upper face of the wiring layer 111.

The inter-layer insulating film is formed by a silicon oxide film, asilicon nitride film, an organic resin or the like, and the wiring layerconsists of wiring whose main component is aluminum or wiring whose maincomponent is copper. The contact is formed, for example, of tungsten,and the via is formed of tungsten or integrally with wiring whose maincomponent is copper. The wiring layer 111 includes connection portions314A and 311A, and is formed of wiring whose main component is copper.The wiring layer 109 is formed of wiring whose main component isaluminum. The pad 313 is arranged in the same layer as the wiring layer109, and contains aluminum as the main component. The wiring layer, thecontact layer, the inter-layer insulating film, and the pad can beformed by an common semiconductor process, and a detailed descriptionthereof will be omitted. By the above process, the configuration asillustrated in FIG. 4B is obtained. In FIG. 4B, the components that aredenoted by numerals 104′, 105, 106, and 108 through 111 later constitutethe wiring structure 149 of FIG. 1. The connection portion 311A laterconstitutes the connection portion 311.

Next, the process for manufacturing the second member 309 of FIG. 1 willbe described with reference to FIG. 5. In FIG. 5, the component laterconstituting the second member 309 of FIG. 1 is denoted by numeral 309′,and the portions later constituting the pixel part 301, the peripheralcircuit part 302, the pad part 312, and the protection diode circuit 315are denoted by numerals 304′, 302′, 312′, and 315′.

First, a semiconductor substrate is prepared, and elements are formed onthe semiconductor substrate. A semiconductor substrate 404 of athickness D4 having a main face 405 and a back-side face 406 isprepared. And, an element separation structure 136 is formed on thesemiconductor substrate 404 using the LOCOS structure, the STI structureor the like. Further, p-type wells 135 and 139 and an n-type well 142are formed in the semiconductor substrate 404. After this, n-typesemiconductor regions 138 and 141 that may constitute a source/drainregion constituting a transistor, a p-type semiconductor region 144, anda semiconductor region constituting a diode are formed. And, a gateelectrode layer 128 including the gate electrodes 137, 140, and 143 ofthe transistor and wiring (resistor) is formed by deposition of a polysilicon layer and patterning. Regarding the method of forming the gateelectrode, the element separation structure, and the semiconductorregion, it is possible to adopt a common semiconductor process, and adetailed description thereof will be omitted. By the above process, theconfiguration of FIG. 5A can be obtained.

Next, a wiring structure is formed on the main face 405 of thesemiconductor substrate 404. The wiring structure has inter-layerinsulating films 124 through 127, contact layers 129, 131, and 133, andwiring layers 130, 132, and 134. The inter-layer insulating film 124covers the gate electrode layer 128, the contact layer 129 is arrangedin the inter-layer insulating film, 124, and the wiring layer 130 isarranged on the inter-layer insulating film 124. Further, theinter-layer insulating film 125 covers the wiring layer 130, the contactlayer 131 is arranged in the inter-layer insulating film 125, the wiringlayer 132 is arranged on the inter-layer insulating film 125, and theinter-layer insulating film 126 covers the wiring layer 132 and isarranged on the inter-layer insulating film 125. And, the contact layer133 is arranged in the inter-layer insulating film 126, the wiring layer134 is arranged on the inter-layer insulating film 126, and theinter-layer insulating film 127 is arranged on the inter-layerinsulating film 126 and has an opening through which the wiring of thewiring layer 134 is exposed. The upper face of the wiring structure isformed by the upper face of the inter-layer insulating film 127 and theupper face of the wiring layer 134.

The inter-layer insulating film is a silicon oxide film. It may also beformed of a silicon nitride film, organic resin or the like. The wiringlayer is composed of wiring whose main component is aluminum or wiringwhose main component is copper. The wiring layer 134 includes aconnection portion 314B and 311B, and is formed by wiring whose maincomponent is copper. Regarding the method of forming the wiring layer,the contact layer, and the inter-layer insulating film, it is possibleto adopt a common semiconductor process, and a detailed descriptionthereof will be omitted. By the above process, the construction of FIG.5B can be obtained. In FIG. 5B, the components indicated by numerals 124through 127, 129 through 134, etc. later constitute the first wiringstructure 150 of FIG. 1. Further, the connection portion 311B laterconstitutes the connection portion 311.

The first member 308′ and the second member 309′ illustrated in FIGS. 4Band 5B are bonded to each other such that the main face 402 and the mainface 405 of the respective semiconductor substrates are opposed to eachother. Specifically, the uppermost face of the wiring structure of thefirst member 308′ and the uppermost face of the wiring structure of thesecond member 309′ are bonded to each other. The connection portions311A and 311B and the connection portions 314A and 314B are formed ofwirings whose main component is copper, so that the bonding can beeffected through copper metal bonding.

After the first member 308′ and the second member 309′ have been bondedto each other, the back-side face 403 side of the semiconductorsubstrate 401 of the first member 308′ is thinned. The thinning can beeffected by chemical-mechanical polishing (CMP), etching or the like.And, the semiconductor substrate 401 is turned into the semiconductorsubstrate 407, with the thickness being changed from D3 to D1 (D1<D3)(FIG. 6A). By thus thinning the semiconductor substrate 401 into thesemiconductor substrate 407, it is possible later to allow the incidentlight to efficiently enter the photoelectric conversion element.Further, at this time, the thickness D1 of the semiconductor substrate407 is smaller than the thickness D4 of the semiconductor substrate 404(D1<D4).

Next, a planarization layer 409 consisting of resin, a color filterlayer 410, a planarization layer 411 consisting of resin, and a microlens layer 412 in this order are formed on the back-side face 408 of thesemiconductor substrate 407. Regarding the method of producing theplanarization layers, the cooler filter layer, and the micro lens layer,it is possible to adopt a common semiconductor process, and a detaileddescription thereof will be omitted. Here, the micro lens layer may beformed up to the region of 312′ constituting the pad part. By the aboveprocess, the construction of FIG. 6B is obtained.

And, an opening 100 for exposing the pad 313 is formed. Here, usingphotolithography, a photoresist mask having an arbitrary opening isprovided on the micro lens layer 412. And, by using dry etching, themicro lens layer 412, the flattened layer 411, the color filter layer410, the flattened layer 409, the semiconductor substrate 407, and theinter-layer insulating film 104′ are removed to form the opening 100 forexposing the pad 313.

And, the micro lens layer 118, the planarization layers 117 and 115, thecolor filter layer 116, the first substrate 101, and the inter-layerinsulating film 104 are formed. In this way, the configuration of FIG. 1is obtained. The semiconductor substrate 404, the main face 405, theback-side face 406, and the thickness D4 of FIG. 6B respectivelycorrespond to the second substrate 121, the main face 122, the back-sideface 123, and the thickness D2 of FIG. 1.

Here, there is no change between the thickness D4 and the thickness D2;however, it is also possible to thin the semiconductor substrate 404 sothat the thickness D2 may be smaller than the thickness D4 (D2<D4). Thethinning involves an increase in the number of steps, but it helps toachieve a reduction in the size of the solid-state imaging device.

As described above, the etching for exposing the pad is conducted fromthe back-side face 408 side of the thinned semiconductor substrate 407,whereby it is possible to shorten the requisite time for the etching forpad formation. Further, the pad 313 can be formed by the same step asthe wiring of the wiring layer 109, enabling to achieve a reduction inman-hours. And, as in the present exemplary embodiment, the pad 313 canbe formed of a metal whose main component is aluminum to achieve areduction in the connection resistance with the external terminal. Atthe time of etching, the pad 313 can also function as an etchingstopper.

In the present invention, the manufacturing method is not restricted tothe process described above, but allows modification in the order ofsteps. The order in which the first member 308 and the second member 309are produced can be set as appropriate. Further, it is also possible topurchase the first member 308 and the second member 309 and to bond themto each other. Further, silicon-on-insulator (SOI) substrates areapplicable as the semiconductor substrates 401 and 402.

In the present exemplary embodiment, the second substrate 121 is thickerthan the first substrate 101. By providing the protection diode circuit315 on such a thick substrate, propagation of voltage fluctuation in thesubstrate due to external noise is mitigated, enabling to reduce theinfluence of external noise.

The second exemplary embodiment of the present invention will bedescribed with reference to FIGS. 7A and 7B. FIGS. 7A and 7B areschematic sectional views of a solid-state imaging device each of whichcorresponds to FIG. 1. In FIGS. 7A and 7B, the components that are thesame as those of FIG. 1 are denoted by the same reference numerals, anda description thereof will be omitted.

The present exemplary embodiment differs from the first exemplaryembodiment in an opening 700 in FIG. 7A and an opening 702 and a pad 701in FIG. 7B. In the present exemplary embodiment, there are provided theopening 700 and the opening 702, which are deeper than that of the firstexemplary embodiment, and there is provided the pad 701, which is closerto the main face 122 of the second member 309 than in the firstexemplary embodiment. In this way, the pad may be arranged at anyposition so long as it is arranged on the first member 308 side of themain face 122 of the second member 309. However, by arranging the pad inproximity to the second member 309 as in the present exemplaryembodiment, it is possible to reduce the connection resistance of thepad as compared with the first exemplary embodiment. In the presentexemplary embodiment also, the protection diode is arranged on thesecond substrate.

Further, in FIG. 7B, the configuration of the opening 702 is differentfrom that of the opening 100 of the first exemplary embodiment. Asillustrated in FIG. 7B, the unnecessary inter-layer insulating film andsemiconductor substrate may be removed.

The pad 701 is arranged in the same layer as the wiring layer 134 of thesecond member 309. Here, the term “the same layer” means a layer whichis formed by the same process or a layer of which the height from themain face to the bottom face or the upper face of the member is thesame. The pad 701 is included in the same layer as the wiring layer 134,and is formed by the same process. Although in the present exemplaryembodiment there is adopted wiring whose main component is copper as inthe first exemplary embodiment, it is more desirable to adopt wiringwhose main component is aluminum for the wiring layer 134 since it isthe same layer as the pad 701. In this case, the connection portion 311may be bonded by a micro bump or the like.

As in the present exemplary embodiment, at no matter what position thepad 701 may be arranged, the protection diode circuit 315 is arranged onthe second substrate. Owing to this construction, it is possible tosuppress incorporation of external noise into the photoelectricconversion element from the pad 701. Further, in the present exemplaryembodiment also, by providing the protection diode circuit 315 on athick substrate, the propagation of voltage fluctuation in the substratedue to external noise is mitigated, thereby enabling to achieve areduction in the influence of external noise.

The third exemplary embodiment of the present invention will bedescribed with reference to FIGS. 8A through 8C. FIG. 8C is a schematicsectional view of a solid-state imaging device of the present exemplaryembodiment; the diagram corresponds to FIG. 1. FIGS. 8A and 8B areschematic sectional views for illustrating a method of manufacturing thesolid-state imaging device of the present exemplary embodiment; thediagrams correspond to FIGS. 6A and 6B. In FIGS. 8A through 8C, thecomponents that are the same as those of FIGS. 6A and 6B are denoted bythe same reference numerals, and a description thereof will be omitted.

The present exemplary embodiment differs from the first exemplaryembodiment in the construction of an opening 811 and of a protectionfilm 806 in FIG. 8C. The protective film 806 of the present exemplaryembodiment covers the side wall (side face) of the first substrate 101having the opening 811. Owing to providing the protection film 806, itis possible to suppress intrusion of water into the device from theopening 811. When an external terminal for connecting to the pad 313comes into contact to a conductive body such as the first substrate,leakage is generated. The protection film 806 prevents the externalterminal from coming into contact with a conductive body, and suppressesgeneration of leakage. Further, the protection film of the presentexemplary embodiment is also arranged on the incidence surface of thephotoelectric conversion portion of the pixel part 301 (that is, theback-side face 103 of the first substrate 101), and also can function asa reflection prevention film. Since the protection film 806 is provided,the configuration of the opening differs from that of the firstexemplary embodiment. Further, the configuration of a planarizationlayer 807, of a color filter layer 808, of a planarization layer 809,and of a micro lens layer 810 may also be changed into differentconfiguration from that of the first exemplary embodiment.

The manufacturing method of the present exemplary embodiment will bedescribed with reference to FIGS. 8A and 8B. The portion of the methodup to the stage of FIG. 6A of the first exemplary embodiment is the sameas that described above, so a description thereof will be omitted. Anopening 800 is formed in the semiconductor substrate 407 of FIG. 6A byphotolithography and etching to form the first substrate 101. Theopening 800 is formed to expose the pad 313. After this, a siliconnitride film 801 that can serve as a protection film is formed by aplasma chemical-vapor deposition (CVD) method or the like to cover theside face of the opening 800 and to cover the back-side face 103 of thefirst substrate 101, whereby the construction of FIG. 8A is obtained.

After this, a planarization layer 802, a color filter layer 803, aplanarization layer 804, and a micro lens layer 805 are formed in thisorder. The materials and the manufacturing method are the same as thoseof the first exemplary embodiment. And, an opening 811 is formed. Theopening 811 extends through the silicon nitride film 801, the flattenedlayer 802, the color filter layer 803, the flattened layer 804, and themicro lens layer 805, and exposes the pad 313. Here, the silicon nitridelayer 801, the planarization layer 802, the color filter layer 803, theplanarization layer 804, and the micro lens layer 805 respectivelyconstitute the protection film 806, the planarization layer 807, thecolor filter layer 808, the planarization layer 809, and the micro lenslayer 810. And, the solid-state imaging device as illustrated in FIG. 8Cis produced.

In the present exemplary embodiment also, the protection diode isarranged on the second substrate. Owing to this configuration, it ispossible to suppress incorporation of external noise into thephotoelectric conversion element from the pad 313. Further, in thepresent exemplary embodiment also, by providing the protection diodecircuit 315 on a thick substrate, propagation of voltage fluctuation inthe substrate due to external noise is mitigated, enabling to reduce theinfluence of external noise.

The fourth exemplary embodiment of the present invention will bedescribed with reference to FIG. 9. FIG. 9 is a schematic sectional viewof a solid-state imaging device; the diagram corresponds to FIG. 1. InFIG. 9, the components that are similar to those of FIG. 1 are denotedby the same reference numerals, and a description thereof will beomitted.

The present exemplary embodiment differs from the first exemplaryembodiment in that there is adopted a through-type electrode 902 andthat a pad 901 is arranged on the back-side face 134 side of the secondsubstrate 121. The through-type electrode 902 is connected to wiring 903included in the wiring layer 130, and the wiring 903 and the inputterminal IN of the protection diode circuit 315 are formed by the samewiring. Regarding the method of forming the through-type electrode,etc., it is possible to adopt a common semiconductor process, and adescription thereof will be omitted.

As in the first exemplary embodiment, in this construction also, theprotection diode circuit 315 is arranged on the second substrate 121.Thus, also in the configuration of the present exemplary embodiment, itis possible to reduce external noise.

As an application example of the solid-state imaging devices of theabove-described exemplary embodiments, an imaging system with asolid-state imaging device incorporated therein will be described. Theterm imaging system covers not only an apparatus such as a camera mainlyintended for photographing, but also an apparatus equipped with aphotographing function as an auxiliary function (e.g., a personalcomputer and a personal digital assistant). For example, a cameraincludes a solid-state imaging device according to the present exemplaryembodiment, and a processing unit configured to process signals outputfrom the solid-state imaging device. This processing unit may include,for example, an A/D converter, and a processor configured to processdigital data output from the A/D converter.

As described above, in the solid-state imaging device of the presentinvention, it is possible to suppress incorporation of external noisefrom the pad. Although in the above-described exemplary embodiments aprotection diode circuit is adopted as an example of the protectioncircuit provided for the second substrate 121 to suppress incorporationof external noise, this should not be construed restrictively; the sameeffect can be attained by using a protection circuit employing atransistor.

The present invention is not restricted to the construction as describedin this specification; it is also possible, for example, to change aconductive type and a circuit to a reverse conductive type. Further,although in the above exemplary embodiments the connection portionconsists of the wiring of a wiring layer, it may consist of any otherstructure so long as it allows securing conduction; thus, it may also bea via or a micro bump. Further, the constructions of the above exemplaryembodiments may be combined with each other as appropriate.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all modifications, equivalent structures, and functions.

This application claims priority from Japanese Patent Application No.2010-149484 filed Jun. 30, 2010, which is hereby incorporated byreference herein in its entirety.

REFERENCE SIGNS LIST

-   -   301 pixel part    -   302 peripheral circuit part    -   308 first member    -   309 second member    -   149 first wiring structure    -   150 second wiring structure    -   312 pad part    -   313 pad    -   315 protection diode circuit    -   101 first substrate    -   121 second substrate    -   100 opening    -   X bonding interface

The invention claimed is:
 1. A solid-state imaging device comprising: afirst semiconductor substrate having a pixel part and a peripheralcircuit part, the pixel part including a photoelectric conversionelement and a first transistor for transferring a charge of thephotoelectric conversion element, and the peripheral circuit partincluding a circuit element of a first circuit; a second semiconductorsubstrate having a second transistor of a second circuit; a wiringstructure arranged between the first semiconductor substrate and thesecond semiconductor substrate; and a pad configured to connect thesolid-state imaging device to an external terminal; wherein the secondsemiconductor substrate has a protection circuit connected to the padand to the second circuit, and wherein the pad is connected to theprotection circuit via the wiring structure, and a semiconductor regionof the second transistor and a semiconductor region of the protectioncircuit are disposed in the second semiconductor substrate.
 2. Thesolid-state imaging device according to claim 1, wherein the protectioncircuit is a protection diode circuit.
 3. The solid-state imaging deviceaccording to claim 1, wherein a plurality of pads and protectioncircuits are arranged.
 4. The solid-state imaging device according toclaim 1, wherein the protection circuit has at least two diodes.
 5. Thesolid-state imaging device according to claim 1, wherein the protectioncircuit has at least one diode and one resistor.
 6. The solid-stateimaging device according to claim 1, wherein the protection circuit issurrounded by an element separation structure.
 7. The solid-stateimaging device according to claim 1, wherein the protection circuit isarranged inwardly with respect to the pad in planar direction.
 8. Thesolid-state imaging device according to claim 1, wherein the pad isarranged to overlap the protection circuit in planar direction.
 9. Asolid-state imaging device comprising: a first semiconductor substratehaving a pixel part and a peripheral circuit part, the pixel partincluding a photoelectric conversion element and a first transistor fortransferring a charge of the photoelectric conversion element, and theperipheral circuit part including a circuit element of a first circuit;a second semiconductor substrate having a second transistor of a secondcircuit; a wiring structure arranged between the first semiconductorsubstrate and the second semiconductor substrate; and a pad configuredto connect the solid-state imaging device to an external terminal;wherein the second semiconductor substrate has a protection circuitconnected to the pad and to the second circuit, wherein the wiringstructure includes a plurality of wiring layers, and wherein the pad isarranged in a layer that is identical with one wiring layer of theplurality of wiring layers, the one wiring layer being arranged betweenthe first semiconductor substrate and the second semiconductorsubstrate.
 10. The solid-state imaging device according to claim 9,wherein a main component of the one wiring layer is the same as the maincomponent of the pad, and wherein the plurality of wiring layersincludes another wiring layer whose main component is copper.
 11. Thesolid-state imaging device according to claim 9, wherein the maincomponent of the pad is aluminum.
 12. The solid-state imaging deviceaccording to claim 1, wherein the second semiconductor substrate has anamplification transistor for outputting a signal based on the charge ofthe photoelectric conversion element.
 13. An imaging system comprising:a solid-state imaging device as claimed in claim 1; and a processingunit configured to process a signal output from the solid-state imagingdevice.
 14. The solid-state imaging device according to claim 9, whereinthe plurality of wiring layers include a wiring layer arranged closer tothe first semiconductor substrate than the one wiring layer, and awiring layer arranged closer to the second semiconductor substrate thanthe one wiring layer.
 15. The solid-state imaging device according toclaim 1, wherein the first semiconductor substrate has a scanningcircuit.
 16. The solid-state imaging device according to claim 9,wherein the first transistor is arranged on a main face of the firstsemiconductor substrate, and a diode which forms the protection circuitis arranged on a main face of the second semiconductor substrate. 17.The solid-state imaging device according to claim 1, wherein the secondsemiconductor substrate is thicker than the first semiconductorsubstrate.
 18. The solid-state imaging device according to claim 15,wherein the second semiconductor substrate has a scanning circuit.
 19. Asolid-state imaging device comprising: a first semiconductor substratehaving a pixel part and a peripheral circuit part, the pixel partincluding a photoelectric conversion element and a first transistor fortransferring a charge of the photoelectric conversion element, and theperipheral circuit part including a circuit element of a first circuit;a second semiconductor substrate having a second transistor of a secondcircuit; a wiring structure arranged between the first semiconductorsubstrate and the second semiconductor substrate; and a pad configuredto connect the solid-state imaging device to an external terminal;wherein the second semiconductor substrate has a protection circuitconnected to the pad and to the second circuit, and wherein an opening,through which the external terminal is connected to the pad, is arrangedin the second semiconductor substrate, and is not arranged in the firstsemiconductor substrate.
 20. An imaging system comprising: a solid-stateimaging device as claimed in claim 9; and a processing unit configuredto process a signal output from the solid-state imaging device.